Petrol engines starter bush removal
Question
Any ideas on the best way of removing the starter motor bush on a 2lt air cooled? Have tried using an expanding bolt. What size tap do I need?
Answer 1
Size M12 Use a tap from a tap and die set, I think it's half inch or 13mm this will cut a thread in the copper bush and gradually twist it out, worked for me before. Soak the new bush in oil overnight (or just squeeze oil into it using themba nd fore-finger, it's an oilite bush). Then use a bolt with a nut screwed a little way down and tap it in with a soft hammer, make sure it goes in straight at the start. Buy two bushes so that if your first attempt goes wrong you have a second chance and can learn from the first attempt, they are cheap
TIP: Don't put bushes in the tool box - they are very soft and will get trashed..
Answer 2
Screw extractor number 6 or 18/25 size (imperial) works a treat for bush removal, only needs the slightest twist (left hand thread) to bite in then bush pulls out easily (did so on a relativley un-worn bush with lots to bite into). Also can be used to fit new bush, lightly bite the extractor into the bush to hold it the starter motor hole as square as you can, and push in (small mirror and light helps to check) then reverse the screw extractor to remove it leaving the bush seated. Tap it home GENTLY with the square reverse end, maybe a wooden dowel would do it better so as not to damage the bush.
The M12 tap definately works as I just removed the bush on mine. There was hardly anything left of it but the tap grabbed it ok and with perseverence removed it in sections. I got the very last bit from the bottom of the hole by chopping it with a sharp screwdriver and prying it out. The idea with the bolt and nut to tap the new bush in worked fine also. I used the top starter bolt and the tiniest hammer I have.
Screw the nut on so that the bolt end comes flush with the end of the bush then you will feel it hit the bottom of the hole when the bush is fully installed as you can't see it at all. Removing the heater pipework from the exchanger on the drivers side helped a lot with my aircooled as space to work is very limited.
See also replace starter motor page
General Thread Taps and Dies
